[1]} pointed out that there should be supermassive black holes in every massive galaxy. [2]} argued that the present-day masses of these black holes had to be consistent with the energy radiated by accretion onto the black holes over the history of the universe. Although this argument is conceptually simple, obtaining the appropriate numbers is complicated. In a detailed study of the Sołtan argument [3]} find that an average Eddington ratio of 50% is needed (see their Figure 7). This favours higher Eddington ratios and supports the larger bolometric corrections implied by reddening corrections such as what we find for NGC 5548.
